Conduits for hydraulic devices



Nov. 7, 1961 J. REITMAN CONDUITS FOR HYDRAULIC DEVICES Filed Jan. 21. 1959 INVENTOR LESTER J. REITMAN ATT NEY United States Patent O 3,001,446 CONDUITS FOR HYDRAULIC DEVICES Lester J. Reitman, Long Beach, N.Y., assignor to Sperry Rand Corporation, a corporation of Delaware Filed Jan. 21, 1959, Ser.I No. 788,227 2 Claims. (Cl. 121-41) This invention relates to hydraulic actuators and more particularly to means for for-ming conduits between spaced portions ofa' hydraulic actuator.

Previously, when it was desired to provide a conduit between spaced portions of a hydraulic actuator, a passage was drilled between the spaced portions. When the spaced portions are relatively close together, this can be readily accomplished. However, when the portions are spaced at a considerable distance from each other and particularly when the metal through which the passage is to be drilled is hardened for high temperature operation or other reasons, drilling the passage between the spaced portions becomes a very difficult land expensive task. To avoid this problem, the prior art also discloses the use of piping connecting the spaced portions which is externm to the hydraulic actuator. This expedient results in a bulky and cumbersome hydraulic unit with the external'piping subject to leakage caused by vibration and maltreatment, particularly when extremely high pressure fluids are conveyed through the external piping.

The problem becomes aggravated when the hydraulic actuator hastwo parts, one of which is movable with respect to the other, and it is desired to convey high pressure fluid from one part to lthe other part or to each of the parts. The only solution prior to the instant inven tion necessitated connections for pressure and return fluidon each part of the hydraulic actuator as well as kexible hosing between the parts or between the part and the source of pressure iluid. Flexible hoses are undesirable because they are prone to leakage and induce undesired coercive `forces which must be overcome to position the respective parts of the hydraulic actuator. Further, the liexible hoses are bulky and add considerable unnecessary weight as well `as being susceptible to rupture when subjected to hig-hvfluid pressure.

Accordingly, it is a primary object of the present inventionto provide one or more conduits within a hydraulic `actuator between relatively widely spaced first and second portions thereof which may be formed without drilling through the actuator.

I-t is -a further object-of the present invention to provide conduits between iirst and second spaced por-tions of a hydraulic actuator that are compact, sturdy, and will withstand extremely high pressure fluid without deterioration.

It is an additional object of the present invention to provide conduits between spaced portions of one part of a hydraulic actuator that is movable with respect to another part of s-aid actuator so that a minimum of pressure 'and return connections and piping are required.

Another object of the present invention is to provide a hydraulic actuator that is compact, ruggedly constructed and reliable `in operation due to unique means for conveying pressure fluid through the actuator.

iThe present invention overcomes the above problems and achieves the aforementioned objects by providing one -or more conduits disposed entirely within the hydraulic actuator that are formed by la plurality of hollow members coaxially disposed one within the other extending between rst and second portions of theA hydraulic actuator. The adjacent surfaces of the hollow members are spaced in order to form the aforementioned conduits. Preferably, but not necessarily, the hollow members are in the form of axial tubes disposed within LICC the hydraulic actuator and connected between the lirst and second portions thereof.

Other objects and advantages of the present invention will become apparent upon a study of the following disclosure when considered in connection with the accompanying drawings, wherein:

IFIG. 1 is a sectional view of -a multiple-input type of hydraulic actuator in vwhich coaxial tubes form supply and return conduits between lirst and second portions of a part of said actuator;

FIG. 2 is a sectional View taken along lines :2--2 of FIG. 1 showing the coaxial arrangement of the tubes forming the conduits; and

FIG. 3 is ya sectional view of an embodiment of the present invention showing -a plurality of coaxial tubes forming a plurality of supply 'and return conduits.

While the present invention is applicable in many types of devices, an embodiment of the invention will be explained for purposes of example with respect to a multiple-input type of hydraulic actuator which may be adapted for use in -aircraft where .the beneii-ts Ofcompactness, reliability, and minimum weight are particularly advantageous. The multiple-input hydraulic actuator of from the actuator 10 to the source of pressure iluid 11.

by means of return connection 'i4 and ilexible hose 15. The supply and return connections 12 and 114, respectively, are mounted on the secondary actuator I16 or irst part of hydraulic lactuator 101. Passages 20 and .21 through the secondary actuator 16 connect supply and return connections L2 and 14, respectively, to a second part, generally indicated as 22, of actuator `lil. The second part 22 of actuator 10 includes a hollow cylindrical piston rod 23 and a main piston 24 integral therewith. The cylindrical piston rod 23 has 4an 4axis of revolution 28.

Main piston 24 is disposed toy slide within a main cylinder 25 that, in turn, is fixed with respect to the airframe 26-by being bolted thereto. The lpiston rod 23 of part 22 extends exteriorly of both ends of main cylinder 25. One extremity of the piston rod 23 may be connected by lug 32 to the elevator of `an airplane, for example, to control the movement thereof as indicated by the legend. The other extremity or irst portion 27 of the piston rod 23 is adapted to slide within ya bore 30 of secondary actuator 16 thus making the second part 22 movable with respect to the first part or secondary actuator 16 of hydraulic lactuator 10. I'he second pant 22 has a second portion 31 thereof in relatively widely spaced relation to the iirst portion 27. In the embodiment shown in FIG. l, the second portion 31 of part 22 includes a pressure uid utilization apparatus in the form of a primary control valve spool 33 slidably disposed in a cylinder 34 of valve sleeve 35, all of which are coaxially mounted with respect to and within the hollow piston rod 23. The lug 32 is screwed into one extremity of the piston rod 23 and secures valve sleeve 35 xed with respect to the piston rod 23. The rightvuard portion of valve sleeve l315 has cylindrical stair-step shoulders 43, 414 and 45 of decreasing diameter cut therein for reasons to be explained.

At the other extremity of piston rod 23, i.e., the first portion 27 thereof, a cylindrical support member 36 is securely screwed to the interior of the piston rod 23 and is coaxial therewith. The leftward portion of support member 36 has cylindrical stair-step shoulders 40, 41 and 42 of decreasing diameter cut therein which correspond to those of valve sleeve 35. Thus, shoulders 40, 41 and 42 of support member 36 have diameters equal to those of corresponding shoulders 43, 44 and 45 of valve sleeve 35, respectively, to support tubes 50 and 51 which are connected between support member 36 and valve sleeve 35. One extremity of tube 50 is supported on shoulder 4i) of support 'member 36 while its other extremity is supported on the corresponding shoulder 43 of valve sleeve 35. One extremity of tube 51 is supported on shoulder 42 of support member 36 while its other extremity is supported on the corresponding shoulder 45 of valve sleeve 35. A

Referring now to FIGS. l and 2, tubes 50 and 51 are so disposed that each has its axis of revolution coincident with the axis of revolution 28 of piston rod 23. Tubes and 51 are coaxially disposed one Within the other and within hollow cylindrical piston rod 23. Each of the hollow members 23, 5t), and 51 is in spaced relation radially with respect to the `adjacent member thereby providing conduits between the adjacent surfaces of members 23, 5i) and 51. Thus, a supply conduit 52 is provided between the adiacent surfaces of piston rod 23 and tube Sil between the first and second portions 27 and 31, respectively, of part 22, while a similar return conduit 53 is formed by the adjacent surfaces of tubes 50 and 5i. To form a conduit, for example, conduit 53, the innermost member 51 of a pair of members 50, 51 has an outside diameter that is less than the inside diameter of the other member 50 of said pair 50, 51 so that the adjacent surfaces of said pair 50, 51 are spaced with respect to each other lalong their entire length.

Preferably, the radial dimensions of each of the tubes are such that a close iit is obtained between the inside of the tube andthe shoulders upon which it is supported, for example, the inside diameter of tube 51 is approximately equal to the diameter of shoulders 42 and 45. Further, the outside diameter of tube 51 is preferably equal to the diameter of shoulders 41 and 44 in order to provide a flush, continuous conduit surface.

In certain applications of the present invention, it may be desirable to use O-ring seals mounted in the shoulders to form uid seals between the inside of the tube and the shoulders upon which the tube is supported. In addition to providing a iluid seal, the use of O-ring seals allows the tolerances between the mating parts to be relaxed since the ilexible O-ring will compensate for minor discrepancies.

As shown in FIG. l, passage 60 connects one extremity of supply conduit 52 to passage 20 while passage 61 connects one extremity of return conduit 53 to passage 21. Passage 62 connects the other extremity of supply conduit 52 to the cylinder 34 Within valve sleeve 35. Passage 62 also connects to the piston of emergency by-pass valve 63. Passage 64 connects the cylinder 34 to the other extremity of return conduit 53. When uncovered by the lands of valve spool 33, passages 65 and 66 connect the cylinder 34 to the right and left-hand portions, respectively, of the main cylinder 25.

One extremity of the valve spool 33 is connected by rod 67 to a cylindrical projection 70 of secondary actuator 16. Support member 36 is centrally bored to receive the cylindrical projection 70 of the secondary actuator 16 and slides thereon.

Within the secondary actuator 16, a secondary control valve spool 71 is disposed to slide Within cylinder 72. Valve spool 71 is connected to be stroked by torque motor 73 in accordance with electrical signals which may be received from an automatic pilot as indicated by the legend. Passage 74 connects passage 20 to cylinder 72 while passage 75 connects cylinder '72 to passage 21. When uncovered by the lands of valve spool 71, passages 76 and 77 connect the cylinder 72 to the right and lefthand portions of the secondary control cylinder 80. Secondary piston 81 is disposed to slide within the secondary control cylinder 80. One extremity of secondary piston 81 is connected to a manual input lug 482 which, in turn, may be connected to receive manual inputs from the control stick as indicated by the legend. Potentiometer 83 is fixed with respect to secondary actuator 16 while the slider arm thereof is connected to lug 82 so that the relative displacement of the lug `82 with respect to the secondary actuator 16 may be measured and provide a feedback signal to the automatic pilot as indicated by the legend.

The multiple-input hydraulic actuator of FIG. 1 may be operated in manual, manual-boost or automatic modes of operation similar to that described with respect 4to the multiple-input hydraulic actuator of the aforementioned patent application S.N. 580,957, now Patent lNo. 2,936,- 135. For purposes of describing the operation of the instant invention, the hydraulic actuator of FIG. l will be described with respect to an automatic mode only. An electrical signal is received from the automatic pilot by torque motor 73 and strokes valve spool 71 to the right, for example. This action ports pressure fluid from source 11 through hose 13, connection 12, passages 20 and 74, through cylinder 72, into passage 76 and the right-hand portion of cylinder 80. Due to the internal friction in the mechanical linkage between lug 82 and the control stick (not shown), piston 81 remains stationary and the pressure fluid in the right-hand portion of cylinder 80 moves secondary actuator 16 to the right, as viewed in the drawing. Fluid is exhausted from the left-hand portion of cylinder 80, through passage 77, cylinder 72, passages and 21, return connection 14 and hose 15 back to source 11, where the iluid is recirculated.

Movement of secondary actuator 16 to the right also moves primary control valve spool 33, which is connected thereto, to the right. This allows pressure Iiluid to be ported from source 11 through hose 13, connection 12, passages 20 and 60, conduit 52, passage 62, through cylinder 34, passage 66 and into the left-hand portion of cylinder 25. With cylinder 25 iixed with respect to the airframe, the second part 22 is moved to the right, as viewed in the drawing. At the same time, fluid is exhausted from the right-hand portion of cylinder 25 into passage 65, through cylinder 34, into passage 64, conduit 53, passages 61 and 62, connection 14, hose 15 and thence to source 11, where it is recirculated. The movement of part 22 to the right also positions the elevator (not shown) accordingly, since it is connected to lug 32 of part 22. An electrical signal of the opposite phase will move the secondary valve spool 71 to the left, which, by a similar sequence of events, will drive the elevator in the opposite direction.

IIn the automatic mode, manual inputs from the control stick may be superimposed upon the electrical inputs from the automatic pilot in order to control the elevator in accordance with the algebraic sum-mation of the two inputs. One method of providing the above is to connect the output of potentiometer 83 in feedback fashion to a summing ampliiier (not shown) which is also connected to receive the output of the automatic pilot. The output of the summing amplifier is connected to control the torque motor 73. Then, when the control stick is moved, lug 82 will also be moved and will position the slider arm o-f potentiometer 83 accordingly. The output signal of the potentiometer 83 is algebraically summed with the signal from the automatic pilot in the summing ampliiier. The output from the summing amplifier controls the torque motor 73 to stroke the valve spool 71 in accordance with the composite signal. 'By a sequence of operations similar to that described above, the elevator is positioned in accordance with the electrical signal 'from the automatic pilot and the mechanical signal from the control stick.

From the foregoing, it will be appreciated that the present invention provides conduits of any desired length that are inexpensive, compact, rugged and not subject to deterioration or leakage. To provide conduits` of tht? length required in the hydraulic actuator of FIG. 1 by drilling through the hardened steel piston rod 23, would be -an extremely expensive and diflicult task. The prior art alternative would be to provide additional supply and return connections on part 22 which would be connected by additional supply and return ilexible hosing to the source of pressure lluid 11 or tothe secondary actuator 16. By eliminating the need for the additional supply and return connections and hosing, the present invention minimizes the weight of the actuator, eliminates the coercive forces caused by the additional flexible hosing and minimizes the possibility of leakage and rupture of the flexible hosing.

Although the invention has been described with respect to right circular cylindrical tubes, it is within the scope of the present invention to form the conduits by tubes having other shapes, such as square, hexagonal or any other suitable conliguration.

Referring now to FIG. 3, an embodiment of the present invention is shown which provides a plurality of supply and return conduits. This is accomplished by mounting a plurality of tubes coaxially one within the other, depending upon the number of supply and return conduits desired. Thus, for example, tubes 90, 91, 92 and 93 are mounted on corresponding cylindrical shoulders of spaced elements such as valve spool 35 and support member 36 in a manner similar to that shown in lFIG. 1. This larrangement forms two supply conduits 94 and 95 and two return conduits 96 and 97. Any number and any combination of supply yand return conduits can be provided by suitably increasing the number of coaxial tubes and suitably connecting the supply and return passages.

To simplify the drawings, O-rings and other leakage prevention devices have not been shown. However, it is understood that they could -be used in a conventional manner to prevent leakage where necessary.

iWhile the invention has been described in its preferred embodiment, it is to be understood that the words which -have been used are words of description rather than limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

l. A hydraulic actuator comprising first land second movable parts and a stationary main cylinder, said second part including a main piston slidably disposed within said main cylinder, said second part further including va hollow cylindrical piston rod integral with said main pis.- ton and extending exteriorly from both ends of said main cylinder, one end of said piston rod being adapted to be connected to a member to be controlled, the other end of said piston rod being disposed to slide within said first part, supply and return connections for pressure fluid mounted on said first part, means including hydraulic means disposed within said iirst part and connected to said supply `and return connections for cont-rolling the moyement of said lirst part in accordance with the algebraic summation of a plurality lof signals, fluid fdow control means within said hollow pis-ton rod and connected to said first part for controlling the ttlow of pressure iluid t0 said main cylinder in accordance 'with the movement of said first part whereby the member to be controlled is controlled in accordance with the algebraic summation of said signals, and conduit rmeans for conveying pressure fluid between said fluid llow control means and said supply 'and return connections, said last-mentioned means including hollow tubes coaxially disposed one within the other and within said hollow piston rod, the adjacent surfaces of said piston rod and said tubes being spaced to provide conduits therebetween, said piston rod and said tubes providing conduits for at least a portion of the distance between said uid ow control means 'and said supply and return connections.

2. In a hydraulic Iactuator as claimed in claim 1 wherein said conduit means includes rst .and second tubes coaxially nested one within the other and wit-hin said hollow piston rod, the adjacent surfaces of said piston rod and said tubes being spaced to provide conduits therebetween, said piston rod and said first tube providing a conduit for at least a portion of the distance between said supply connection and said iluid flow control means, and said first tube and said second tube providing a conduit for at least a portion of the distance between said fluid ilow control means and said return connection.

References Cited in the file of this patent UNITED STATES PATENTS 2,633,102 lBaldwin etal Mar. 31, 1953 2,693,243 Strandell et al. Nov. 2, 1954 2,705,940 Edwards Apr. 12, 1955 2,810,370 Fox et al. Oct. 22, 19,57 FOREIGN PATENTS 749,564 Great Britain May 30, 1956 

